Adsorption of polyatomics: Theoretical approaches in model systems and applications

Abstract

The adsorption of polyatomics on one- and two-dimensional lattices is studied by combining theoretical modeling, Monte-Carlo (MC), simulations and their correspondence with experimental results. In one dimension, the rigorous statistical thermodynamics of interacting chains has been presented. With respect to two-dimensional adsorption, six different models to study non-interacting adsorbates have been discussed: (i) an extension to two dimensions of the exact thermodynamic functions obtained in one dimension; (ii) the Flory-Huggins's approximation and its modification to address linear adsorbates; (iii) the well-known Guggenheim-DiMarzio approximation; (iv) the fourth one is a new description of adsorption phenomena, based on Haldane's fractional statistics; (v) the so-called Occupation Balance, based on the expansion of the reciprocal of the fugacity; and (vi) a simple semi-empirical model obtained by combining exact one-dimensional calculations and Guggenheim-DiMarzio approach. In addition, the statistical thermodynamics of interacting polyatomics has been developed on a generalization in the spirit of the Bragg-Williams and the quasi-chemical approximations. Comparison with MC simulations and experimental adsorption isotherms are used to test the accuracy and reliability of the proposed models. Finally, applications to heterogeneous systems and multilayer adsorption are discussed.